Mexican football officials are blaming contaminated meat for five of their national team players failing doping tests.

The Mexican Football Federation said the players had all tested positive for the banned substance clenbuterol from tests carried out in Mexico on May 21. Clenbuterol can be used to speed up and increase muscle mass in animals.

The five Mexicans were not allowed to play in their CONCACAF Gold Cup first round match against Cuba in Charlotte, North Carolina Thursday night. Mexico got off to a slow start but seized control and won 5-0, clinching a quarterfinal berth in the North, Central America and Caribbean regional tournament being played in the United States.

A number of athletes, including three-time Tour de France cycling champion Alberto Contador, have blamed their positive test results on eating meat adulterated with the steroid.

Hector Gonzalez, Mexican football federation director of national teams, said the players had eaten tainted beef at Mexico's High Performance Centre where the team prepared to defend its Gold Cup title.

Gonzalez said Mexican farming officials were looking into beef supplies at the center. He said the players were to undergo more testing Friday in Los Angeles at a certified laboratory, which he said would “surely be negative.”

Gonzalez said Mexico had appealed to be allowed to call up five replacements, a request that was to be dealt with by Gold Cup organizers at a meeting on Friday.

Among the five players testing positive were PSV Eindhoven defender Francisco Rodriguez and goalkeeper Guillermo Ochoa, two starters for Mexico in last year's World Cup.